Breast implants are commonly used to replace or augment breast tissue. Typically, such implants are made from a shell of soft and flexible biocompatible material which is filled with a fluid, such as a saline solution, or a polysiloxane or a silicone gel.
It is naturally desirable for a breast implant to match the weight and feel of the tissue being replaced or augmented. Implants which have saline solution as the filler material have been lacking in this regard because the saline solution tends to flow too freely within the implant, thereby reducing the naturalness of the implant's feel. Saline-containing implants also have a disadvantage in that leaks in the outer shell or in the valving mechanism can occur which lead to the undesirable spread of the filler medium within the body as well as deflation of the implant itself. In some implants, saline solution has been replaced with a gel to more closely resemble the feel of the tissue and to reduce the adverse effects of leakage.
It has also been known to incorporate various interior structures within the implant in addition to or in lieu of liquid as filler for the implant. For instance, U.S. Pat. No. 5,246,454 to Peterson discloses a breast implant in which flat, disc shaped pouches filled with saline solution comprise the interior structure of the implant. Also, U.S. Pat. Nos. 5,007,940, 5,116,387 and 5,158,573 to Berg disclose the use of discrete polymeric bodies as tissue replacement material. The polymeric bodies may be injected into the body to form an in situ implant, or may be used as filler within an outer implant shell. The bodies are made of silicone rubber or a water swellable hydrogel, specifically a partially hydrolyzed polyacronitrile, and are described to have reversible deformity of about 20 to 75% of their unstressed outer diameter and a lubricious surface.
There is a need for an improved breast implant which will retain the natural feel of the tissue being replaced, and which will also substantially reduce or eliminate the probability of leakage. Ideally, the implant will also not deflate if a leak should occur in the outer shell of the implant. The present invention is directed toward meeting these needs.